package org.liulinlin.sejw.db;

import java.io.*;
import java.sql.*;
import java.util.*;
import java.util.Date;

public class DBConnectionManager {
	static private DBConnectionManager instance;		//唯一实例
	static private int clients;
	
	private Vector<Driver> drivers = new Vector<Driver>();
	private PrintWriter log;
	private Hashtable<String, DBConnectionPool> pools = new Hashtable<String, DBConnectionPool>();
	
	static synchronized public DBConnectionManager getInstance() {
		if (instance == null) {
			instance = new DBConnectionManager();
		}
		clients++;
		return instance;
	}
	private DBConnectionManager() {
		init();
	}
	private void init() {
		InputStream is = getClass().getResourceAsStream("db.properties");
		Properties dbProps = new Properties();
		try {
			dbProps.load(is);
			System.out.println("读取数据成功！");
		} catch (Exception e) {
			System.err.println("不能读取属性文件。" + "请确保db.properties在CLASSPATH指定的路径中");
			return;
		}
		String logFile = dbProps.getProperty("logfile", "DBConnectionManager.log");
		System.out.println(logFile);
		try {
			log = new PrintWriter(new FileWriter(logFile, true), true);
		} catch (IOException e) {
			System.err.println("无法打开日志文件：" + logFile);
			log = new PrintWriter(System.err);
		}
		loadDrivers(dbProps);
		createPools(dbProps);
	}
	public void freeConnection(String name, Connection con) {
		DBConnectionPool pool = (DBConnectionPool) pools.get(name);
		if (pool != null) {
			pool.freeConnection(con);
		}
	}
	public Connection getConnection(String name) {
		DBConnectionPool pool = (DBConnectionPool) pools.get(name);
		if (pool != null) {
			return pool.getConnection();
		}
		return null;
	}
	public Connection getConnection(String name, long time) {
		DBConnectionPool pool = (DBConnectionPool) pools.get(name);
		if (pool != null) {
			return pool.getConnection(time);
		}
		return null;
	}
	public int getClient() {
		return clients;
	}
	public synchronized void release() {
		if (--clients != 0) {
			return;
		}
		
		Enumeration<DBConnectionPool> allPools = pools.elements();
		while (allPools.hasMoreElements()) {
			DBConnectionPool pool = (DBConnectionPool) allPools.nextElement();
			pool.release();
		}
		/*
		Enumeration<Driver> allDrivers = drivers.elements();
		while (allDrivers.hasMoreElements()) {
			Driver driver = (Driver) allDrivers.nextElement();
			try {
				DriverManager.deregisterDriver(driver);
				log("撤销JDBC驱动程序" + driver.getClass().getName() + "的注册");
			} catch (SQLException e) {
				log("无法撤销下列JDBC驱动程序的注册：" + driver.getClass().getName());
			}
		}
		*/
	}
	private void createPools(Properties props) {
		Enumeration propNames = props.propertyNames();
		while (propNames.hasMoreElements()) {
			String name = (String) propNames.nextElement();
			if (name.endsWith(".url")) {
				String poolName = name.substring(0, name.lastIndexOf("."));
				String url = props.getProperty(poolName + ".url");
				if (url == null) {
					log("没有为连接池" + poolName + "指定URL");
					continue;
				}
				String user = props.getProperty(poolName + ".user");
				String password = props.getProperty(poolName + ".password");
				String maxconn = props.getProperty(poolName + ".maxconn", "0");
				
				int max;
				try {
					max = Integer.valueOf(maxconn).intValue();
				} catch (NumberFormatException e) {
					log("错误的最大连接数限制：" + maxconn + ".连接池：" + poolName);
					max = 0;
				}
				DBConnectionPool pool = new DBConnectionPool(poolName, url, user, password, max);
				pools.put(poolName, pool);
				log("成功创建连接池" + poolName);
			}
		}
	}
	private void loadDrivers(Properties props) {
		String driverClasses = props.getProperty("drivers");
		StringTokenizer st = new StringTokenizer(driverClasses);
		while (st.hasMoreElements()) {
			String driverClassName = st.nextToken().trim();
			try {
				Driver driver = (Driver) Class.forName(driverClassName).newInstance();
				DriverManager.registerDriver(driver);
				drivers.addElement(driver);
				log("成功注册JDBC驱动程序" + driverClassName);
			} catch (Exception e) {
				log("无法注册JDBC驱动程序：" + driverClassName + "，错误：" + e);
			}
		}
	}
	private void log(String msg) {
		log.println(new Date() + ":" + msg);
	}
	private void log(Throwable e, String msg) {
		log.println(new Date() + ":" + msg);
		e.printStackTrace(log);
	}
	
	class DBConnectionPool {
		private int checkedOut;
		private Vector<Connection> freeConnections = new Vector<Connection>();
		private int maxConn;
		private String name;
		private String password;
		private String URL;
		private String user;
		
		public DBConnectionPool(String name, String URL, String user, String password,
				int maxConn) {
			this.name = name;
			this.URL = URL;
			this.user = user;
			this.password = password;
			this.maxConn = maxConn;
		}
		
		public synchronized void freeConnection(Connection con) {
			freeConnections.addElement(con);
			checkedOut--;
			notifyAll();
		}
		public synchronized Connection getConnection() {
			Connection con = null;
			if (freeConnections.size() > 0) {
				con = (Connection) freeConnections.firstElement();
				freeConnections.removeElementAt(0);
				try {
					if (con.isClosed()) {
						log("从连接池" + name + "删除一个无效连接");
						con = getConnection();
					}
				} catch (SQLException e) {
					log("从连接池" + name + "删除一个无效连接");
					con = getConnection();
				}
			} else if (maxConn == 0 || checkedOut < maxConn) {
				con = newConnection();
			}
			if (con != null) {
				checkedOut++;
			}
			return con;
		}
		public synchronized Connection getConnection(long timeout) {
			long startTime = new Date().getTime();
			Connection con;
			while ((con = getConnection()) == null) {
				try {
					wait(timeout);
				} catch (InterruptedException e) {
					
				}
				if ((new Date().getTime() - startTime) >= timeout) {
					return null;
				}
			}
			return con;
		}
		public synchronized void release() {
			Enumeration<Connection> allConnections = freeConnections.elements();
			while (allConnections.hasMoreElements()) {
				Connection con = (Connection) allConnections.nextElement();
				try {
					con.close();
					log("关闭连接池" + name + "中的一个连接");
				} catch (SQLException e) {
					log(e, "无法关闭连接池" + name + "中的连接");
				}
			}
			freeConnections.removeAllElements();
		}
		private Connection newConnection() {
			Connection con = null;
			try {
				if (user == null) {
					con = DriverManager.getConnection(URL);
				} else {
					con = DriverManager.getConnection(URL, user, password);
				}
				log("连接池" + name + "创建一个新的连接");
			} catch (SQLException e) {
				log(e, "无法创建下列URL的连接：" + URL);
				return null;
			}
			return con;
		}
	}
}
